This invention relates to actuating apparatus for a bicycle derailleur, of the type comprising a geared motor unit with an output shaft and a driven shaft rotationally connected to said output shaft.
Studies and researches in the field of electrically operated actuators for controlling the rear derailleur and/or the front derailleur of a bicycle have multiplied in recent years.
The Applicant previously presented U.S. patent application Ser. No. 09/920,763, describing an actuating apparatus for controlling the front derailleur of the type above, in which the output shaft of the geared motor unit is rotationally connected to a driven shaft, comprising a worm screw meshing a geared sector forming a single part with one of the articulated arms in the articulated parallelogram system which connects, according to the conventional technique, the fork element of the front derailleur to the fixed support body fastened to the frame of the bicycle.
In order to simplify and expedite the assembly of the previously proposed apparatus, this invention relates to an actuating apparatus of the type described at the beginning of this description, characterised in that said driven shaft is connected to the output shaft of the geared motor unit by means of a coupling, which ensures a limited misalignment between the axis of the geared motor output shaft and the axis of the driven shaft.
Thanks to this characteristic, the device according to this invention can be easily fitted, without needing to ascertain whether the axes of the geared motor output shaft and the driven shaft coincide perfectly.
In a preferred form of embodiment, said coupling is an Oldham coupling, comprising a cylindrical body with two end faces, presenting coupling surfaces with ends facing the output shaft of the geared motor unit and the driven shaft, shaped so to allow a misalignment of the axes of said shafts. Preferably, said cylindrical body of the Oldham coupling presents two housings in the shape of reciprocally orthogonal diametral slots, slidingly receiving two axial appendixes projecting from the facing ends of the two shafts connected by the coupling.
The invention is particularly applied to a geared motor unit of the type described in U.S. patent application Ser. No. 09/953,285. As described in this application, the geared motor unit comprises an electrical motor, which body is connected to a fixed supporting body of the derailleur, and a reducer, comprising an epicyclic gear, to which output shaft an angular position sensor of said shaft is associated. This sensor is a rotary potentiometer sensor sending a signal indicating the angular position of the geared motor output shaft to an electronic control unit aboard a bicycle, which cuts off the operation of the electrical motor following the cyclist""s command to shift the derailleur to a certain operative position.